Various mechanisms exist to allow computers and executing software applications to programmatically interact. For example, remote procedure call (“RPC”) protocols have long existed that allow a program on one computer to cause a program on another computer to be executed, and various object-oriented architectures such as CORBA (“Common Object Request Broker Architecture”) and DCOM (“Distributed Component Object Model”) provide similar capabilities. In addition, a variety of middleware programs have been implemented to connect separate applications (often of distinct types and from unrelated sources) to allow communication. For example, various EDI (“Electronic Data Interchange”) networks exist that provide standard mechanisms to allow a computer system of one user of the network to send data to a computer system of another user of the network.
The widespread popularity of the World Wide Web (“Web”) has provided additional opportunities for computers to inter-communicate. For example, much current Web use involves users interactively requesting Web pages from Web servers (e.g., via executing Web browser applications of the users) and receiving the requested information in response. In addition to such interactive user specification of requested information, there is also growing use of the Web to support the programmatic interaction of remote applications to exchange information via defined APIs (“application program interfaces”), such as via Web services.
Web services allow heterogeneous applications and computers to interact, and can be defined and implemented using a variety of underlying protocols and techniques. For example, some Web service implementations return data in XML (“eXtensible Markup Language”) format using HTTP (“HyperText Transport Protocol”) in response to a Web service invocation request specified as a URI (“Uniform Resource Identifier”), such as a URL (“Uniform Resource Locator”) that includes a specified operation and one or more query parameters. In other implementations, additional underlying protocols are used for various purposes, such as SOAP (“Simple Object Access Protocol”) for standard message exchange, WSDL (“Web Services Description Language”) for description of service invocations, and UDDI (“Universal Description, Discovery, and Integration service”) for discovery of available services.
Although Web services allow various applications and computers to interact, the current implementations and uses of Web services have various limitations. For example, while some providers of Web services are willing to make their Web services available for free, the most useful and reliable Web services are often not freely available. Unfortunately, the mechanisms for providers of Web services and potential consumers of those Web services to agree upon payment and other terms for transactions can be time-consuming and difficult to use. Moreover, there may often be issues of security and trust that hinders such agreements, such that potential consumers may lack sufficient assurance that prospective Web service providers will reliably and accurately provide desired Web services, while Web service providers may lack assurance that their Web services will be used only by authorized consumers and only in accordance with any conditions specified by the providers. In addition, application developers may be reluctant to have their application programs invoke fee-based Web services if they cannot limit and control the use of such Web services by end-users of the application programs who would be making the calls to those Web services. Finally, easy-to-use mechanisms do not typically exist to allow Web service providers to collect specified payment for the use of their Web services by consumers.
Thus, it would be beneficial to provide a solution that addresses these and other problems associated with the use of Web services and/or that otherwise facilitates the interaction of computer systems and executing applications.